48 follow
49 were you doing 
50 had eaten 
51 invites 
52 got
53 am having 
54 has risen 
55 have gone
56 comes/ will tell
57 go/ am staying 
58 is going to rain 
59 doesn't have 

41. The man got out of the car, walked round to the back and opened the book.
43. My teacher is explaining the lessobut I don't understand what he is saying.
48. An economic crisis often follows the war.
51. She invites me to lunch with her once or twice a year.
52.They had sold them all the books when we got there.
53. Where are ? - I'm upstairs. I am having a bath.